Modular motor assembly

ABSTRACT

Embodiments of a modular motor assembly are disclosed. In some embodiments, a motor comprises a plurality of modular magnetic units, where each of the modular magnetic units includes at least one rotor and at least one stator. The motor further comprises a plurality of structural segments each adapted to support a stator of a corresponding one of the modular magnetic units, where each of the structural segments interlocks with a next structural segment to form a stack. A method of manufacturing a motor includes arranging a selected number of modular magnetic units, coupling the selected number of modular magnetic units to a shaft, coupling the selected number of modular magnetic units to respective structural segments, and forming electrical connections to apply three-phase voltage to stator windings of the modular magnetic units.

CROSS REFERENCE TO OTHER APPLICATIONS

This application is a continuation of co-pending U.S. patent applicationSer. No. 15/893,383 entitled MODULAR MOTOR ASSEMBLY filed Feb. 9, 2018which is incorporated herein by reference for all purposes.

BACKGROUND OF THE INVENTION

Electric motors operate by converting electrical energy to mechanicalenergy. Depending on the application for the electric motor (e.g., lawnmower, land vehicle, aircraft, etc.), the number of magnetic unitsmaking up the electric motor can be varied to provide the desired amountof mechanical power. Motors are typically custom-made for specific uses.Parts may need to be replaced during the lifetime of the motor. Themanufacture and maintenance of a motor can be costly because of thecustom-made nature of the motor, diversity of parts used, and thequalification of parts. Manufacturing and maintenance costs may escalateif the motor is especially complex and has many unique parts.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention are disclosed in the followingdetailed description and the accompanying drawings.

FIG. 1 is a perspective view of an embodiment of a modular motorassembly.

FIG. 2 is cross-sectional side view of an embodiment of a modular motor.

FIG. 3A is a cross-sectional view of an embodiment of a magnetic unitfor a modular motor assembly.

FIG. 3B is an exploded view of an embodiment of a magnetic unit for amodular motor assembly.

FIG. 4 shows an example of a structural segment for a modular motorassembly according to embodiments of the present disclosure.

FIG. 5 is a block diagram illustrating an embodiment of an endplate fora modular motor assembly.

FIG. 6A shows an example of shaft spacer for a modular motor assemblyaccording to embodiments of the present disclosure.

FIG. 6B is a perspective cross-sectional view of an example of shaftspacer placement in a modular motor assembly according to embodiments ofthe present disclosure.

FIG. 6C is cross-sectional side view of an example of shaft spacerplacement in a modular motor assembly according to embodiments of thepresent disclosure.

FIG. 7A is perspective cross-sectional view of a shaft for a modularmotor assembly according to embodiments of the present disclosure.

FIG. 7B is cross-sectional side view of a shaft for a modular motorassembly according to embodiments of the present disclosure.

FIG. 8 is a block diagram illustrating an embodiment of a motor and fanassembly 800 in which a modular motor is provided.

FIG. 9 is a block diagram illustrating an example of an aircraft inwhich a modular motor assembly is provided.

FIG. 10 is a flow chart illustrating an embodiment of a process formanufacturing a modular motor.

DETAILED DESCRIPTION

The invention can be implemented in numerous ways, including as aprocess; an apparatus; a system; a composition of matter; a computerprogram product embodied on a computer readable storage medium; and/or aprocessor, such as a processor configured to execute instructions storedon and/or provided by a memory coupled to the processor. In thisspecification, these implementations, or any other form that theinvention may take, may be referred to as techniques. In general, theorder of the steps of disclosed processes may be altered within thescope of the invention. Unless stated otherwise, a component such as aprocessor or a memory described as being configured to perform a taskmay be implemented as a general component that is temporarily configuredto perform the task at a given time or a specific component that ismanufactured to perform the task. As used herein, the term ‘processor’refers to one or more devices, circuits, and/or processing coresconfigured to process data, such as computer program instructions.

A detailed description of one or more embodiments of the invention isprovided below along with accompanying figures that illustrate theprinciples of the invention. The invention is described in connectionwith such embodiments, but the invention is not limited to anyembodiment. The scope of the invention is limited only by the claims andthe invention encompasses numerous alternatives, modifications andequivalents. Numerous specific details are set forth in the followingdescription in order to provide a thorough understanding of theinvention. These details are provided for the purpose of example and theinvention may be practiced according to the claims without some or allof these specific details. For the purpose of clarity, technicalmaterial that is known in the technical fields related to the inventionhas not been described in detail so that the invention is notunnecessarily obscured.

An electric motor may include electrical windings and be adapted togenerate a magnetic field that interacts with the permanent magnets oradditional electrical windings to produce torque. The motor is usuallycustom-designed to be specific size and to output a desired amount ofpower. For example, different shafts and housings are machined to be aspecific length according to specifications of the motor.

Custom-made motors often have many different types of parts (sometimescalled “components”). The parts may be made by different manufacturers.A part needs to be qualified to determine compatibility with mechanicaldevices and monitor the quality of the part. This ensures thatcomponents made by different manufacturers are compatible with themechanical devices. The qualification of parts can be a lengthy andbureaucratic process. This can slow the development and maintenance ofmotors and the vehicles in which they are used. Additionally, themanufacturing of many unique parts sometimes requires tooling orequipment specific to individual parts, increasing cost. One way toimprove the manufacture and maintenance of motors is to reduce thenumber of unique parts used.

Embodiments of a modular motor assembly are described. The motor can beconstructed from a series of modular magnetic units that have a modularstructure comprising structural segments held together by interlockingfeatures and connections such as bolts. In various embodiments, a motorincludes a plurality of modular magnetic units, wherein each of themodular magnetic units includes at least one rotor and at least onestator, and a plurality of structural segments each adapted to support astator of a corresponding one of the modular magnetic units, where eachof the structural segments interlocks with a next structural segment toform a stack. At build time, a variable number of modular magnetic unitscan be combined to make a motor have two or more stages. For instance,the modular magnetic units can be identical or substantially identicalin that the modular magnetic units share a common part. This has thebenefit of, among other things, needing fewer part for a motor.

FIG. 1 is a perspective view of an embodiment of a modular motorassembly. Motor 100 is a single stack motor with six magnetic units. Themotor 100 includes magnetic units 110, structural segments 120-132, andshaft 150. In contrast to conventional motors, in various embodiments,the complex portions of the shaft is made common by means of common endslinked by a variable number of spacers. This reduces the cost ofmanufacturing and maintaining the motor because fewer different partsmay be used.

Each of the magnetic units 110 is adapted to generate force when theunit's magnetic field interacts with its winding currents. In this view,a few of the magnetic units 110 are visible through the windows formedby the spokes of end piece structural unit 120. The outermost magneticunit is 110. The magnetic units are more fully described with respect toFIG. 2, in which all of the magnetic units are visible.

Each of the structural segments 120-132 is adapted to provide supportfor the magnetic units. The structural segments collectively form ahollow tube (sometimes called “canister”) adapted to hold one or moremagnetic units inside the cylinder formed by the structural segments. Invarious embodiments, the structural segments include end structuralsegments 120 and 132 (which may or may not be identical to each other)and internal structural segments 122-130. The internal structuralsegments may be substantially identical to each other. The structuralsegments may be coupled to form an opening, e.g., for electricalconnectors 142. Referring to FIG. 4, area 414 forms half of an openingwhen two structural segments are coupled, a window is formed throughwhich electrical connections may be routed. The structural segments canbe coupled to form a stack by running a pin through pin holes aligned toform long channel 140.

An example of an internal structural segment is more fully describedherein with respect to FIG. 4. An example of an end structural segmentis more fully described herein with respect to FIG. 5. In someembodiments, the structural units may be mechanically coupled to eachother while the magnetic units are removable from motor 100.

Returning to FIG. 1, the shaft 150 is adapted to transfer torquegenerated by the magnetic units to the canister. For example, one ormore magnetic units may be coupled to the shaft. In some embodiments, aselect few of the rotors in the magnetic units may be fixed to theshaft. In some embodiments, the portion of the magnetic unit coupled tothe shaft is connected via splines in the motor. Additional units maycouple to one another using pins and threaded fasteners. The shaft 150is more fully described herein with respect to FIG. 2. Space betweenmagnetic units may be provided by means of one or more shaft spacers. Anexample of a shaft spacer is shown in FIG. 6.

In various embodiments, one or more electrical connections may beprovided. For example, electrical connector 142 allows the magnetic unitto be connected to a power source. The structural segments may bestructured to accommodate the electrical connections as more fullyexplained herein with respect to FIG. 4.

Motor 100 is a multi-stack motor with six magnetic units. In someembodiments (not shown), shaft spacers may be provided vary shaft lengthby making a modular shaft. Shaft spacers may be used to separate onestack of one or more magnetic units from another stack of one ormagnetic units. This allows a desired amount of energy to be provided byselecting an appropriate number of magnetic units and sizing the motoras desired to meet power requirements of the vehicle in which the motoris provided. In some embodiments, a motor having a relatively long shaftmay comprise a few magnetic units by using spacers. In variousembodiments a four-stack motor may be made by shortening the shaftrelative to the one pictured in FIGS. 1 and 2 or making a split stackmotor of substantially the same length as the motor of FIGS. 1 and 2 byreplacing two of the magnetic units with a spacer.

FIG. 2 is a side view of an embodiment of a modular motor. Motor 200includes magnetic units 222-232, structural segment 220, and shaft 250.

Each of the structural segments 220 is adapted to support one or morecorresponding magnetic units. For example, the structural segments maysurround a corresponding magnetic unit. The structural segments are morefully described with respect to FIG. 1.

Each of the magnetic units 222-232 is adapted to generate torque whenthe magnetic unit's magnetic field interacts with its winding currents.In this example, the six magnetic units 222-232 are stacked. Variabletorque may be generated depending on sizing of the magnetic units andnumber of magnetic units are provided in the motor. Typically, moretorque is generated when a motor has more magnetic units. In variousembodiments, magnetic units may be provided in a stacked manner asshown. Torque may be transferred via the shaft to the load to be driven.Here, torque may be transferred from the magnetic units via spokes toshaft 250. Torque may be transferred from the magnetic units to thestructural segments 220. If a plurality of magnetic units are provided,the collective torque may be transferred via the shaft to power avehicle or device in which the motor is provided. Example applicationsfor motor 100 are shown in FIGS. 8 and 9. In various embodiments, an endpiece magnetic unit may be structured differently from an internalmagnetic unit. An example of a magnetic unit is shown in FIGS. 3A and3B.

Shaft 250 accommodates a variable number of magnetic units by varyingthe length of one feature. In this example, the shaft 250 is pictured asbeing substantially uniform in diameter through the length of the motor.In some embodiments, the shaft may instead have a varying diameter. Anexample of a shaft with a variable diameter is shown in FIG. 7. In thisexample, no shaft spacers are provided because motor 200 is a singlestack motor. In some embodiments, one or more magnetic units may beconnected (e.g., bolted to the shaft).

FIG. 3A is a cross-sectional view of an embodiment of a magnetic unitfor a modular motor assembly. The magnetic unit 300 includes rotorhousing 302, stator 306, rotor (not shown), and stator housing 308. Therotors may be implemented by a magnetic array such as a Halbach array.Adjacent magnetic arrays may be attached to a same physical piece butneed not interact magnetically. For example, the magnetic arrays may bemagnetically aligned. This allows, in various embodiments, the magneticunits to be removed from the motor and the remaining magnetic unitswould be compatible with one another. The example upper rotor housing isshown with an output shaft on top.

The stator 306 may include wire winding mounted to the stator housing.For example, the stator may include a wire winding encased infiberglass. In some embodiments, the stator housing may be differentfrom the one shown in FIG. 3A. The stator may have pockets machined intoit to accommodate pins of a structural segment such as pin 404 of FIG.4. The stator may be removably coupled to the structural segment. Forexample, the pockets of the stator allow the stator to sit (sometimesreferred to as “float”) on the pins of the structural segment. Thecoupling of the stator to the structural segment allows torque to betransferred to the canister formed by the structural segments. Thefloating stator transfers torque without needing to be fixedly coupledto adjacent components. A plurality of bearings may control motionbetween the upper rotor and the stator and the lower rotor and thestator.

FIG. 3B is an exploded view of an embodiment of a magnetic unit for amodular motor assembly. The magnetic unit includes upper rotor housing302, upper magnet array 304, stator 306, stator housing 308, lowermagnet array 310, and lower rotor housing 312. Each of the componentsare like their counterparts in FIG. 3A unless otherwise described.

In various embodiments, internal magnetic units differ from end piecemagnetic units. An internal magnetic unit includes the components(including two magnet arrays 304, 310) shown in FIG. 3B, while an endpiece magnetic unit includes a single magnet array. Referring to FIG.3B, an end piece magnetic unit, in various embodiments, comprises rotorhousing 302, magnet array 304, stator 306, and stator housing 308. Asingle stack motor may be formed by joining two end magnetic units.Together, the two end magnetic units comprise two magnet arrays with astator in between.

As mentioned above, an internal magnetic unit has a pair of magnetarrays. Referring to FIG. 3B, an internal magnetic unit comprises upperrotor housing 302, upper magnet array 304, stator 306, stator housing308, lower magnet array 310, and lower rotor housing 312. In someembodiments, the rotor housing and stator housing may be different fromthe housing 302, 308, and 312.

FIG. 4 shows an example of a structural segment for a modular motorassembly according to embodiments of the present disclosure. Inparticular, ring-shaped structural segment 400 is an example of aninternal structural segment for a modular motor. The structural segment400 may be arranged to surround internal magnetic units that areprovided between two end structural segments such as the one shown inFIG. 5.

Structural segment 400 may be adapted to couple to adjacent structuralsegments by a lip and/or a pinhole. For example, the structural segmentsmay be structured to interlock, fit into adjacent structural segments,mate, have features for receiving a next structural segment, or thelike. Lip 412 may be structured to connect to an adjoining structuralunit. For example, lip 412 may be structured to mate with adjacentstructural segments such that when stacked, a group of structuralsegments are locked into place and are not easily displaced.

Pinhole 402 may be adapted to receive a connection such as a pin to anadjoining structural segment. For example, a pin may be provided alongthe length of the motor through each of the pinholes in the structuralsegments to fix the structural segments in place. Referring to FIG. 1, apin is inserted through pinholes in each of structural segments 120-132to join these structural segments at 140.

Structural segment 400 may be adapted to accommodate electricalconnections. As shown, structural segment 400 has an interrupted lip.For example, portion 414, which is a cavity may align with a cavity ofanother structural segment to form an area through which wiring can beextended. In one aspect, the tooth-type lip may facilitate electricalconnections by providing a clearance for wiring.

Pin 404 is adapted to facilitate attachment of a stator of a magneticunit to the structural segment. As more fully described with respect toFIG. 3, a stator may have pockets adapted to rest on the pins 404,thereby removably coupling the stator to the structural segment. Thefloating stator may transfer torque to the canister via this positionwith respect to the structural segment.

One or more windows 406 may be provided in the structural segment. Inone aspect, window 406 may allow air flow. For example, heat generatedby the magnetic units may be dissipated through the window 406. Inanother aspect, window 406 may facilitate monitoring of the motor. Forexample, expected operation such as spinning of the magnetic units maybe observed through the windows provided along the outside wall of thestructural segments. FIG. 5 is a block diagram illustrating anembodiment of an endplate for a modular motor assembly. In particular,structural segment 500 is an example of an end piece for a modularmotor. End structural segment 500 is configured with one or more spokes512 (here, six spokes) to provide support for the motor and support theinternal pieces (magnetic unit). The spokes support bearings that allowa shaft 550 to rotate with respect to the circumference 502 of thestructural segment.

FIG. 6A shows an example of shaft spacer for a modular motor assemblyaccording to embodiments of the present disclosure. The shaft spacer canbe interlocking and held together by a tension bolt or other means. Insome embodiments, several shaft spacers can be stacked to create alarger space between magnetic units. In some embodiments, the shaft canbe secured with a tie bolt at an end piece. For example, center piecesmay have an interlocking coupling and may be secured by providing a tiebolt running through clamps to the end piece. The shaft spacers may fillthe space created when magnetic units are removed. In variousembodiments, each rotor section of a magnetic unit bolts to the next andonly a select few (e.g., end units) bolt to the shaft. This facilitatesremoval of magnetic units because they can be de-coupled from adjacentmagnetic units without needing to also remove them from the shaft.

A motor of a specified dimension may be made with a variable number ofmagnetic units by replacing the space created by the vacated magneticunits with shaft spacers. FIG. 6B is a perspective cross-sectional viewof an example of shaft spacer placement in a modular motor assemblyaccording to embodiments of the present disclosure. FIG. 6C iscross-sectional side view of an example of shaft spacer placement in amodular motor assembly according to embodiments of the presentdisclosure. In the examples of FIGS. 6B and 6C, shaft spacer 602 isplaced hear the center of the shaft to separate unit 604 from unit 606.

FIG. 7A is perspective cross-sectional view of a shaft for a modularmotor assembly according to embodiments of the present disclosure. FIG.7B is cross-sectional side view of a shaft for a modular motor assemblyaccording to embodiments of the present disclosure. The example shaftpictured in FIGS. 7A and 7B includes a plurality of segments. Thesegments may have varying diameters. Here, section 702 has a smallerdiameter than section 704. This allows a shaft of variable cross sectionto be provided. A variable cross section may be suitable for relativelylonger shafts. Longer shafts may more prone to flexing in the middle,for example, because magnetic units may be hollow in the middle. Flexingmay be prevented or reduced by providing a larger cross section in themiddle of the shaft. The length of the shaft and size of the crosssection in the middle of the shaft can be sized according to applicationof the motor. A relatively long shaft or large cross-section is one witha relatively high ration of length to diameter/stiffness/sectionmodulus.

FIG. 8 is a block diagram illustrating an embodiment of a motor and fanassembly 800 in which a modular motor is provided. The motor and fanassembly may be part of an aircraft such as multicopter 900 of FIG. 9.The assembly 800 includes cone 806, fan 804, and motor 802.

The motor 802 may power fan 804 to cause the fan 804 to spin and producethrust. The number of magnetic units provided in the motor can be variedbased on the aircraft's power requirements. For example, a lightaircraft designed to carry a single passenger or a relatively light loadmay be adequately served by a motor having relatively few magneticunits. The magnetic units may provide the desired RPM or thrust. Thecone 806 may be shaped to facilitate aerodynamics of the aircraft inwhich the assembly 800 is provided.

FIG. 9 is a block diagram illustrating an example of an aircraft inwhich a modular motor assembly is provided. Aircraft 900 is amulticopter that uses a modular motor assembly.

In the example shown, the multicopter 900 has two propulsion systems: aforward propulsion system 102 and a vertical propulsion system (notshown). The forward propulsion system 902 is used to propel themulticopter forward along a longitudinal (roll) axis. As shown here, theblades of the lift fans in the forward propulsion system 902 areoriented to rotate in a vertical plane.

The forward propulsion system 902 produces lift to keep the aircraftairborne in a manner similar to a fixed wing aircraft (e.g., where theforward propulsion of the multicopter causes airflow over and under thewings which in turn induces an aerodynamic force upwards on the bottomof the wings). In the exemplary multicopter, the fans of the forwardpropulsion system are implemented using modular motors (variousembodiments of which are described herein).

In the vertical propulsion system, the blades of the lift fans areoriented to rotate in a horizontal plane. The vertical propulsion systemis used to move (e.g., up or down) the aircraft along a vertical (yaw)axis. The vertical propulsion system produces lift in a manner similarto helicopters where the lift is produced by the airflow downwards.

In various embodiments, the shapes and/or pitch angles of the blades inthe forward propulsion system 902 and vertical population system may beoptimized for the specific type of flying (e.g., forward flight versusvertical flight).

While the multicopter is flying, one of the propulsion systems may beturned off (if desired) while the other propulsion system remains on.For example, if the multicopter 900 is flying forward at a constantaltitude, then the vertical propulsion system may be turned off toconserve power and/or because the forward propulsion system 902 is moreefficient at flying in this manner. Or, if the multicopter is hoveringin-air at a constant position, the forward propulsion system 902 may beturned off

FIG. 10 is a flow chart illustrating an embodiment of a process formanufacturing a modular motor. This process may be implemented tofacilitate assembly of the modular motor shown in FIG. 1.

In the example shown, the process begins by arranging a selected numberof modular magnetic units (1002). The number of modular magnetic unitsmay be selected according to a power requirement of a vehicle or devicein which the motor is provided. In some embodiments, the modularmagnetic units may be arranged manually and/or by a robotic arm. Forexample, six magnetic units may be suitable for some multicopterapplications.

The process couples the selected number of modular magnetic units torespective structural segments (1004). The magnetic units may be coupledto structural segments that provide support for the magnetic units andfacilitate integration of the magnetic units. For example, a structuralsegments may be a ring that can be fitted around a magnetic unit toprovide support for the stator of the magnetic unit. Adjacent structuralsegments may be coupled to each other to form a canister containing theselected number of modular magnetic units.

The process couples the selected number of modular magnetic units to ashaft (1006). In some embodiments, all of the magnetic units are coupledto the shaft. In some embodiments, a select few such as the end magneticunits are coupled to the shaft. This may facilitate removal of magneticunits because they can be de-coupled from adjacent magnetic unitswithout needing to also remove them from the shaft. For example, a motorcan be easily adapted from one application to another by removing oradding magnetic units depending on whether power requirements increaseor decrease from one application to the next. Although this example isdescribed with the order of structural coupling followed by shaftcoupling, these steps can be performed in any order.

The process forms electrical connections to apply multi-phase voltage tostator windings of modular magnetic units (1008). In variousembodiments, pre-made buses or bars may be used to make the connections.The types and numbers of buses or bars used may be determined by anumber of magnetic units in the stack. In various embodiments, magnetsforming a magnet array in the modular magnetic units have optimallyoriented magnetization directions throughout the magnets. For example,the sintered grains of the magnet cause the magnet to have a magneticfield like that of a Halbach array.

The modular motor assembly described herein finds application in variousaircraft including forward propulsion systems. For example, a modularmotor (sometimes called a “stackable motor”) has an interlocking design,variable length shaft, and the ability to have a variable number oflayers to accommodate different loads or vehicles. The modular motorassembly described herein can be easily adapted for varying powerrequirements by using different numbers of magnetic units, structuralsegments, and/or shaft spacers. For example, the number of modular partsused can be varied based on needed RPM, torque, and the like. Partsunique to a configuration can be reduced and/or eliminated, thussimplifying and reducing the cost of manufacture and maintenance of amotor.

Although the foregoing embodiments have been described in some detailfor purposes of clarity of understanding, the invention is not limitedto the details provided. There are many alternative ways of implementingthe invention. The disclosed embodiments are illustrative and notrestrictive.

What is claimed is:
 1. (canceled)
 2. A motor comprising: a first modularmagnetic assembly comprising a first rotor assembly and a first statorassembly operable to magnetically induce rotation of the first rotorassembly around a motor axis; a first stator housing to which the firststator assembly is detachably mounted; a second modular magneticassembly comprising a second rotor assembly and a second stator assemblyoperable to magnetically induce rotation of the second rotor assemblyaround the motor axis; a second stator housing to which the secondstator assembly is detachably mounted; one or more intermediate statorhousings coupled with and between the first stator housing and thesecond stator housing to form an annular canister defining an interiorspace in which the first modular magnetic assembly and the secondmodular magnetic assembly are disposed; and a shaft assembly comprisinga shaft and a shaft spacer, wherein the first rotor assembly and thesecond rotor assembly are rotationally coupled to the shaft for rotationwith the shaft around the motor axis, and wherein the shaft spacermaintains a separation distance between the first rotor assembly and thesecond rotor assembly parallel to the motor axis.
 3. The motor of claim2, wherein the first stator housing, the second stator housing, and eachof the one or more intermediate stator housings are identicallyconfigured.
 4. The motor of claim 2, wherein the one or moreintermediate stator housings comprise two or more of the intermediatestator housings.
 5. The motor of claim 4, wherein the one or moreintermediate stator housings comprise three or more of the intermediatestator housings.
 6. The motor of claim 2, wherein: the shaft spacer isremovable to accommodate installation of one or more intermediatemodular magnetic assemblies between the first modular magnetic assemblyand the second modular magnetic assembly; each of the one or moreintermediate modular magnetic assemblies comprises a respectiveintermediate rotor assembly and a respective intermediate statorassembly operable to magnetically induce rotation of the respectiveintermediate rotor assembly around the motor axis; and each respectiveintermediate stator assembly is detachably mountable to a respective oneof the intermediate stator housings.
 7. The motor of claim 2, whereineach of the first stator assembly and the second stator assemblycomprises an electrical connector that extends through a respectiveaperture through the annular canister.
 8. A motor comprising: a firstmodular magnetic assembly comprising a first rotor upper assembly, afirst rotor lower assembly and a first stator assembly, wherein thefirst stator assembly comprises a first stator wire winding operable tomagnetically induce rotation of the first rotor upper assembly and thefirst rotor lower assembly around a motor axis; a first stator housingto which the first stator assembly is detachably mounted; a secondmodular magnetic assembly comprising a second rotor upper assembly, asecond rotor lower assembly and a second stator assembly, wherein thesecond stator assembly comprises a second stator wire winding operableto magnetically induce rotation of the second rotor upper assembly andthe second rotor lower assembly around the motor axis; a second statorhousing to which the second stator assembly is detachably mounted; and ashaft to which the first rotor upper assembly, the first rotor lowerassembly, the second rotor upper assembly and the second rotor lowerassembly are rotationally coupled, wherein the first stator housing andthe second stator housing are configured to interlock to form asubstantially annular canister defining an interior space in which thefirst modular magnetic assembly and the second modular magnetic assemblyare disposed.
 9. The motor of claim 8, wherein: the first rotor upperassembly comprises a first upper rotor housing and a first upper rotorpermanent magnet assembly attached to the first upper rotor housing; thefirst rotor lower assembly comprises a first lower rotor housing and afirst lower rotor permanent magnet assembly attached to the first lowerrotor housing; the second rotor upper assembly comprises a second upperrotor housing and a second upper rotor permanent magnet assemblyattached to the second upper rotor housing; and the second rotor lowerassembly comprises a second lower rotor housing and a second lower rotorpermanent magnet assembly attached to the second lower rotor housing.10. The motor of claim 9, wherein each of the first upper rotorpermanent magnet assembly, the first lower rotor permanent magnetassembly, the second upper rotor permanent magnet assembly and thesecond lower rotor permanent magnet assembly has an annular disk shape.11. The motor of claim 9, wherein each of the first upper rotorpermanent magnet assembly, the first lower rotor permanent magnetassembly, the second upper rotor permanent magnet assembly and thesecond lower rotor permanent magnet assembly comprises a Halbach array.12. The motor of claim 8, further comprising: a first plurality ofbearings configured to control relative motion between the first rotorupper assembly and the first stator wire winding and between the firstrotor lower assembly and the first stator wire winding; and a secondplurality of bearings configured to control relative motion between thesecond rotor upper assembly and the second stator wire winding andbetween the second rotor lower assembly and the second stator wirewinding.
 13. The motor of claim 8, further comprising: a first endmodular magnetic assembly having a first end rotor assembly and a firstend stator assembly, wherein the first end stator assembly comprises afirst end stator wire winding operable to magnetically induce rotationof the first end rotor assembly around the motor axis; a first endstator housing to which the first end stator assembly is detachablymounted; a second end modular magnetic assembly having a second endrotor assembly and a second end stator assembly, wherein the second endstator assembly comprises a second end stator wire winding operable tomagnetically induce rotation of the second end rotor assembly around themotor axis; and a first end stator housing to which the first end statorassembly is detachably mounted, wherein the first end rotor assembly andthe second end rotor assembly are rotationally coupled with the shaft,and wherein the first rotor upper assembly, the first rotor lowerassembly, the second rotor upper assembly, and the second rotor lowerassembly are disposed between the first end rotor assembly and thesecond end rotor assembly.
 14. A motor comprising: a first modularmagnetic assembly comprising a first rotor assembly and a first statorassembly operable to magnetically induce rotation of the first rotorassembly around a motor axis, wherein the first stator assemblycomprises three or more first stator assembly coupling featuresdistributed circumferentially around the first stator assembly; a firststator housing comprising three or more first stator housing statorcoupling features, wherein each of the first stator housing statorcoupling features is adapted to be interfaced with a respective one ofthe first stator assembly coupling features for transfer of torquearound the motor axis from the first stator assembly to the first statorhousing; a second modular magnetic assembly comprising a second rotorassembly and a second stator assembly operable to magnetically inducerotation of the second rotor assembly around the motor axis, wherein thesecond stator assembly comprises three or more second stator assemblycoupling features distributed circumferentially around the second statorassembly; and a second stator housing comprising three or more secondstator housing stator coupling features, wherein each of the secondstator housing stator coupling features is adapted to be interfaced witha respective one of the second stator assembly coupling features fortransfer of torque around the motor axis from the second stator assemblyto the second stator housing, wherein the first stator housing iscoupled with the second stator housing to form an annular canisterdefining an interior space in which the first modular magnetic assemblyand the second modular magnetic assembly are disposed.
 15. The motor ofclaim 14, wherein: the first stator assembly comprises six or more ofthe first stator assembly coupling features distributedcircumferentially around the first stator assembly; the first statorhousing comprises six or more of the first stator housing statorcoupling features; the second stator assembly comprises six or more ofthe second stator assembly coupling features distributedcircumferentially around the second stator assembly; and the secondstator housing comprises six or more of the second stator housing statorcoupling features.
 16. The motor of claim 14, wherein each respectiveinterfacing pair of the first stator assembly coupling features and thefirst stator housing stator coupling features and each respectiveinterfacing pair of the second stator assembly coupling features and thesecond stator housing stator coupling features comprises a protrudingpin aligned parallel with the motor axis and a receptacle shaped toaccommodate and interface with the protruding pin.
 17. The motor ofclaim 14, wherein: the first stator housing comprises three or morefirst stator housing inter-coupling features; and the second statorhousing comprises three or more second stator housing inter-couplingfeatures, wherein respective pairs of one of the first stator housinginter-coupling features and one of the second stator housinginter-coupling features are inter-coupled to couple the first statorhousing with the second stator housing.
 18. The motor of claim 17,wherein each of the first stator housing inter-coupling features andeach of the second stator housing inter-coupling features comprises apinhole aligned parallel with the motor axis for receiving a respectiveconnection pin that forms a connection between the first stator housingand the second stator housing.
 19. The motor of claim 17, wherein eachof the first stator housing inter-coupling features and a respective oneof the first stator housing stator coupling features are adjacentlydisposed and centered on a respective plane on which the motor axis iscoplanar.
 20. The motor of claim 14, wherein: the first stator housinghas a recessed edge that at least partially defines an aperture in theannular canister through which an electrical connector portion of thefirst stator assembly extends; and the second stator housing has arecessed edge that at least partially defines an aperture in the annularcanister through which an electrical connector portion of the secondstator assembly extends.